Adjustable length joist



June 20, 1967 E. A. DEMEULES ET AL 3,325,957

ADJUSTABLE LENGTH JOIST 2 Sheets-Sheet 1 Filed June 10, 1963 INVENTORS fuaE/vEADEMEl/L E6 BY 71 VA. D

EMEl/L E d 10AM 141- roR/vEYs- June 20, 1967 E. A. DEMEULES AL 3,325,957

ADJUSTABLE LENGTH JOIST 2 Sheets-Sheet 2 Filed June 10, 1963 AY/LDEMEUL EJ' United States Patent 3,325,957 ADJUSTABLE LENGTH J OIST Eugene A. Demeules and Jay A. Demeules, Minneapolis, Minn, assignors to Standard Iron & Wire Works, Inc., Minneapolis, Minn., a corporation of Minnesota Filed June 10, 1963, Ser. No. 286,650 6 Claims. (Cl. 52-632) The present invention relates to structural supporting members and more particularly to steel supporting beams and joists of the type which can be lengthened or shortened to suit the requirements of the Work.

Numerous adjustable length beams and joists have been previously proposed. These previous devices have not, however, been entirely satisfactory particularly in the support of concrete pouring forms. Some of these devices include two slidably related members which are approximately equal to each other in length. A significant shortcoming of this arrangement derives from the fact that when this type of beam is extended, it provides a great deal less strength than when collapsed. These beams also weigh more and are therefore more difficult to handle. Moreover, the extent to which the center of the beam is deflected downwardly under loading is dependent upon the amount to which the beam is collapsed. This condition will often cause an undesirable camber in the lower surface of a concrete beam which has been produced in a form supported by such joists.

In still other beams of the type described, a wedge has been used for releasably locking two slidably related beam members in the position selected for use. It is, however, possible for such a wedge to move from the position in which it was placed thereby substantially weakening the connection between the two slidably related parts.

In still other adjustable joists which have been previously proposed, some of the movable sections include a longitudinally extending slot adapted to receive a fastener. In these devices, the relative longitudinal movement between sections has been limited to the length of the slot.

In view of these and other defects of the prior art it is one object of the present invention to provide an improved adjustable joist which makes efficient use of materials, is light in weight, rugged in construction and reliable in operation.

It is yet another object of the present invention to provide an improved adjustable beam which provides substantially the same strength when elongated as when collapsed and will therefore exhibit a predetermined camber when loaded.

Still another object of the present invention is the provision of an improved extensible joist including a plurality of diagonally positioned reinforcing members, an end piece slidably mounted thereon, a cross member extending through the joist between the diagonal members and connected to the end piece and a provision for allowing extension of the end piece a distance greater than the spacing between the diagonal members.

Yet another object of the present invention is the provision of an improved adjustable length joist including a main beam portion, an extension slidably mounted on one end of the main beam portion and a releasable retaining means for reliably forcing the extension into engagement with the main beam portion.

Yet another object of the present invention is the provision of an improved adjustable length beam including a relatively large center portion, a pair of end members mounted for sliding movement upon opposite sides of one end of the beam and a provision for reliably holding the members in engagement with opposite sides of the main beam portion.

It is yet another object of the present invention to provide an improved extensible joist with a main joist member and an end piece including a provision for reliably securing the inward end of the end piece to the upward end of the main joist member.

Other objects of the invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

The invention is illustrated by the accompanying drawings in which the same numerals refer to corresponding parts and in which:

FIGURE 1 is a side elevational view of a joist embodying the present invention;

FIGURE 2 is a partial enlarged view of one end of the joist of FIGURE 1 with the end piece thereof removed;

FIGURE 3 is a perspective -view of the end piece of the present invention;

FIGURE 4 is a partial side elevational view of the joist with the end piece in its extended position;

FIGURE 5 is a view similar to FIGURE 6 but illustrating the end piece in its retracted position; taken on the line 6-6 of FIGURE 5; and

FIGURE 6 is a vertical transverse sectional view taken on the line 66 of FIGURE 5; and

FIGURE 7 is a transverse sectional view taken on the line 77 of FIGURE 5.

Briefly stated, in accordance with the present invention, we provide an extensible joist including a main beam portion and an end piece mounted for sliding move. ment on at least one end thereof. A releasable retainer is provided for securely fastening the end piece to the main beam portion.

According to a preferred form of the invention the end piece comprises a pair of spaced apart elongated members positioned on opposite sides of the main beam and held in position by a fastener extending therebetween and through the main beam portion. A slot is provided in each of the elongated members so that the end piece can be moved longitudinally a distance greater than the cross member moves during extension of the end piece. A fastener is also provided for releasably securing the inward end of the end piece to the upper end of the main beam member.

The invention will be best understood by reference to the accompanying figures wherein the same numerals re fer to corresponding parts in the several views.

Referring now to the figuresthere is shown a joist 10 including a center section 12 formed from a longitudinally extending and laterally spaced and aligned angle irons 14 and 16 between which are securely fastened as by welding to a plurality of diagonally positioned brace members 18. The members 18 comprise segments of a single rod which is bent alternately at selected angles in upward and downward directions. Rigidly secured to the bottom of each of the brace members 18 as by welding is a longitudinally extending st-ress member such as an angle iron 20. The angle iron 20 is oriented so that the sides thereof are inclined upwardly and positioned on opposite sides of the bends between brace members 18. It will be noted by an inspection of FIGURES 6 and 7, that at each bend in the rod forming the braces 18 there is a longitudinally extending arc of rod 22 which transmits forces to the stress member. It has been found in the past that a torsional force was exerted on the stress member due to the longitudinal displacement of the centers of adjacent braces at the point where they cont-act the stress member. We have discovered, however, that when angle iron 20 is employed in accordance with the present invention, this undesirable effect can be reduced since the are 22 is attached to the stress member at its center only.

As can best be seen in FIGURES 4 and 5, the ends of the angle iron 20 are bent upwardly at 24 and extend a short distance at 26 along an axis parallel to the diagonal member 18 at each end. By means of this relatively simple provision, the invention assures an additionally secure joint between member 20 and the last brace 18. Moreover, a rounded corner is provided which helps to reduce the chance that a person may be injured by striking the end ofthe angle iron.

Mounted upon each end of the joist 10 is an end piece or extension 30 comprising a pair of elongated members such as channels 32 and 34 positioned on opposite sides of the center beam member 12. A corner section 36 of eachof the channels 32 and 34 is cut out as best seen in FIGURES 1 through 5. An upwardly inclined and outwardly extending end plate 38 is secured in section 36 by welding the same at one end to the lower edges of each of the channels 32 and 34 and at the other end to the lower edges of the sections 36.

A cross member 40 is also connected between the upper edges of the outer ends of channels 32 and 34 for securing the channels together. It will therefore be understood that the end piece 30 has a generally U-shaped configuration when seen in plan view with the outer ends thereof being rigidly connected together by the end plate 38 and the cross member 40.

When the apparatus is in use, the channel members are positioned in exact lateral alignment and have a predetermined spacing therebetween which corresponds to the spacing between the outside edges of the vertical portions of the irons 14 and 16 as best seen in FIGURES 6 and 7. Thus, until the end piece 30 is secured in position 'as will be described hereinbelow, it can be slid longitudinally of the main beam member 10 as a single unit.

At the approximate center of each of channels 32 and 34 is a longitudinally disposed and elongated slot 50;

Adjacent the outside of each slot 50 is a rectangular washer 51 having a central opening therein. The slots 50 in each of channels 32 and 34 are aligned so that a retaining element or cross member such as a bolt 52 can be positioned to extend between the channels 32 and 34 and through the openings in the washers 51 with a nut 54 fastened to the threaded end thereof. As can be clearly seen in FIGURES 4 and 5, the bolt 52 is positioned below the irons 14 and 16 and between the last two diagonal brace members 18. As a result, the longitudinal movement of bolt 52 will be limited by the spacing between the upper ends of the last two brace members 18. By the provision of a slot 50, we enable the end piece 30 to be moved a greater distance than the spacing between the upper ends of the brace members 18 or in other words, a greater distance than the bolt 52 is allowed to move. The motion of end piece 30 is therefore not limited by the spacing between brace members and this is accomplished without modifying or in any way reducing the strength of the center beam portion 12.

When the end pieces 30 are to be fully extended, the bolt 52 should be moved to the inward end of the slots 50 and the nut 54 securely tightened thereby forcing the channels 32 and 34 tightly against the vertical web of the irons 14 and 16. In this manner the end piece 30 is securely retained in the desired position.

When the end piece 30 is to be retracted to its innermost position, the nut 54 is first loosened on the bolt 52 on the channels 32 and 34 and are slid inwardly to the position of FIGURE As this is done, the bolt 52 will slide to the outer end of the slots 50 and 52 as shown in FIGURE 5. The nut 54 can then be retightened so as to securely press the channels 32 and 34 against the vertical portions of irons 14 and 16.

As best shown in FIGURES 4, 5 and 6, a retaining member such as a vertically disposed bolt 60*is operatively connected between the main beam 12 and the end piece 30 for securely supporting the inward end of the end piece 30 against downward movement with respect to the center beam 12. The bolt 60 is rigidly secured at its upward end to the irons 1'4 and 16 as by welding and is provided with screw threads 62 at its lower end. A laterally disposed support member in the form of bar 64 is mounted loosely upon the lower end of the bolt 60 beneath the channels 32 and 34. A nut 66 is threaded upon the bolt 60 beneath the member such as a channel 64 including upwardly turned ends 64a and 64b to help prevent the members 32 and 34 from spreading when the end piece is fully extended and for securely retaining it against the lower edges of the channels 32 and 34.

It will be understood that when the end piece 30 is to be moved, the bolt 66 must be loosened to allow the channels 32 and 34 to slide freely with respect to the bolt 60. When the channel or end piece 30 is moved to its desired position, the nut 66 can again be tightened thereby forcing the member 64 into contact with the channels 32 and 34. The upper ends of the channels will in turn be forced against the horizontally disposed webs of the irons 14 and 16. The inward portion of the extension 30 is in this manner reliably held against downward movement a with respect to the center beam portion 12.

The end pieces 30 while they may vary considerably in length and height are preferably substantially shorter than the length of the center portion 12 and for this reason, very efiicient use of materials is accomplished. Also, while the height of the end pieces 30 can be varied, we prefer to employ end pieces 30 which are somewhat less than one-half the height of the center beam portion 12. This can readily be accomplished with our invention since we provide retaining member 60 for supporting the inward end of the extension 30 from the top of the center beam portion 12 rather than supporting the inward end of the extension 30 upon the lower edge of the beam 12.

Numerous structural units embodying the present invention have been manufactured and sold. These units have been used very successfully under actual service conditions and were found to be rugged in construction and reliable in operation. A very efficient use of materials was also realized since the end pieces 30 did not merely add dead weight to the beam but also provided additional strength. Moreover, the end piece 30* could be moved longitudinally a distance greater than the spacing between the upper ends of the brace members 18 without modifying or reducing the strength of the beam 12.

It is apparent that many modifications and variations of this invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

What is claimed is:

1. An extensible joist comprising in combination: a main joist assembly composed of a pair of longitudinally extended laterally spaced elongated members, each elongated member having an outwardly directed flange and a downwardly directed flange, a brace means including an elongated element having alternate upward and.

downward right angle bends, said elongated element having alternate right angle bends located between and secured to said downwardly directed flanges to divide said element into a plurality of segments, a longitudinally extended stress member positioned below said members and secured to said brace means, and end piece having a generally U-shaped configuration mounted on one end of said joist assembly for longitudinal sliding movement thereon, said end piece comprising a pair of end piece members positioned adjacent the outside of one end of said downwardly directed flange of said elongated member at the outer end thereof and a cross member connecting the outer ends of the end piece members, each end piece member having an elongated top surface engageable with the bottom surface of the adjacent outwardly directed flange of said elongated member and a side engageable with the outside of the adjacent downwardly directed flange, said end piece members including opposed and aligned longitudinally extended openings, and adjustable and releasable fastening means extended through said openings between adjacent segments of said brace means releasably clamping the sides of the end piece members into engagement with the downwardly directed flanges, a single retaining means connected to said elongated members longitudinally inwardly from said one end of the joist assembly and extended downwardly therefrom between said end piece members, said retaining means having a portion engaging the bottom of said end piece members and holding the top surfaces of the end piece members in engagement with the bottom surfaces of the downwardly directed flanges.

2. The joist defined in claim 1 wherein the longitudinally extended stress member is an angle iron welded to alternate bends in the elongated element.

3. The joist defined in claim 1 wherein said releasable fastening means includes a nut and bolt assembly extended through the longitudinal opening in said end piece members.

4. The joist defined in claim 1 wherein each end piece member is channel shaped in cross-section.

5. The apparatus according to claim 1 in which the longitudinally extended stress member bends upwardly at each end thereof and extends a short distance along an axis parallel to the segment of said elongated element nearest the end of said joist.

6. The apparatus according to claim 1 wherein said retaining means comprising a vertically disposed bolt welded at its upper end to said downwardly directed flange of the elongated members, a supporting member positioned below said end piece and a nut for raising said support member into contact with said end piece to securely retain the upward surface of said end pieces in contact with said elongated members.

References Cited UNITED STATES PATENTS 1,563,118 11/1925 Tonnelier 52632 X 1,620,293 3/ 1927 Schenck 52-694 1,911,018 5/1933 Goeltz 52-694 X 3,221,461 12/1965 Grunfeld 52-632 X FOREIGN PATENTS 840,435 6/ 1952 Germany. 810,081 12/ 3 Germany.

FRANK L. ABBOTT, Primary Examiner.

RICHARD W. COOKE, JR., Examiner. 

1. AN EXTENSIBLE JOIST COMPRISING IN COMBINATION: A MAIN JOIST ASSEMBLY COMPOSED OF A PAIR OF LONGITUDINALLY EXTENDED LATERALLY SPACED ELONGATED MEMBERS, EACH ELONGATED MEMBER HAVING AN OUTWARDLY DIRECTED FLANGE AND A DOWNWARDLY DIRECTED FLANGE, A BRACE MEANS INCLUDING AN ELONGATED ELEMENT HAVING ALTERNATE UPWARD AND DOWNWARD RIGHT ANGLE BENDS, SAID ELONGATED ELEMENT HAVING ALTERNATE RIGHT ANGLE BENDS LOCATED BETWEEN AND SECURED TO SAID DOWNWARDLY DIRECTED FLANGES TO DIVIDE SAID ELEMENT INTO A PLURALITY OF SEGMENTS, A LONGITUDINALLY EXTENDED STRESS MEMBER POSITIONED BELOW SAID MEMBERS AND SECURED TO SAID BRACE MEANS, AND END PIECE HAVING A GENERALLY U-SHAPED CONFIGURATION MOUNTED ON ONE END OF SAID JOIST ASSEMBLY FOR LONGITUDINAL SLIDING MOVEMENT THEREON, SAID END PIECE COMPRISING A PAIR OF END PIECE MEMBERS POSITIONED ADJACENT THE OUTSIDE OF ONE END OF SAID DOWNWARDLY DIRECTED FLANGE OF SAID ELONGATED MEMBER AT THE OUTER END THEREOF AND A CROSS MEMBER CONNECTING THE OUTER ENDS OF THE END PIECE MEMBERS, EACH END PIECE MEMBER HAVING AN ELONGATED TOP SURFACE ENGAGEABLE WITH THE BOTTOM SURFACE OF THE ADJACENT OUTWARDLY DIRECTED FLANGE OF SAID ELONGATED MEMBER AND A SIDE ENGAGEABLE WITH THE OUTSIDE OF THE ADJACENT DOWNWARDLY DIRECTED FLANGE, SAID END PIECE MEMBERS INCLUDING OPPOSED AND ALIGNED LONGITUDINALLY EXTENDED OPENINGS, AND ADJUSTABLE AND RELEASABLE FASTENING MEANS EXTENDED THROUGH SAID OPENINGS BETWEEN ADJACENT SEGMENTS OF SAID BRACE MEANS RELEASABLY CLAMPING THE SIDES OF THE END PIECE MEMBERS INTO ENGAGEMENT WITH THE DOWNWARDLY DIRECTED FLANGES, A SINGLE RETAINING MEANS CONNECTED TO SAID ELONGATED MEMBERS LONGITUDINALLY INWARDLY FROM SAID ONE END OF THE JOIST ASSEMBLY AND EXTENDED DOWNWARDLY THEREFROM BETWEEN SAID END PIECE MEMBERS, SAID RETAINING MEANS HAVING A PORTION ENGAGING THE BOTTOM OF SAID END PIECE MEMBERS AND HOLDING THE TOP SURFACES OF THE END PIECE MEMBERS IN ENGAGEMENT WITH THE BOTTOM SURFACES OF THE DOWNWARDLY DIRECTED FLANGES. 